A Facile Li_(2)TiO_(3) Surface Modification to Improve the Structure Stability and Electrochemical Performance of Full Concentration Gradient Li-Rich Oxides

Full concentration gradient lithium-rich layered oxides are catching lots of interest as the next generation cathode for lithium-ion batteries due to their high discharge voltage,reduced voltage decay and enhanced rate performance,whereas the high lithium residues on its surface impairs the structure stability and long-term cycle performance.Herein,a facile multifunctional surface modification method is implemented to eliminate surface lithium residues of full concentration gradient lithium-rich layered oxides by a wet chemistry reaction with tetrabutyl titanate and the post-annealing process.It realizes not only a stable Li_(2)TiO_(3)coating layer with 3D diffusion channels for fast Li^(+)ions transfer,but also dopes partial Ti^(4+)ions into the sub-surface region of full concentration gradient lithium-rich layered oxides to further strengthen its crystal structure.Consequently,the modified full concentration gradient lithium-rich layered oxides exhibit improved structure stability,elevated thermal stability with decomposition temperature from 289.57℃to 321.72℃,and enhanced cycle performance(205.1 mAh g^(-1)after 150 cycles)with slowed voltage drop(1.67 mV per cycle).This work proposes a facile and integrated modification method to enhance the comprehensive performance of full concentration gradient lithium-rich layered oxides,which can facilitate its practical application for developing higher energy density lithium-ion batteries.

Electrolyte Concentration Regulation Boosting Zinc Storage Stability of High-Capacity K0.486V2O5 Cathode for Bendable Quasi-Solid-State Zinc Ion Batteries

Vanadium-based cathodes have attracted great interest in aqueous zinc ion batteries(AZIBs)due to their large capacities,good rate performance and facile synthesis in large scale.However,their practical application is greatly hampered by vanadium dissolution issue in conventional dilute electrolytes.Herein,taking a new potassium vanadate K0.486V2O5(KVO)cathode with large interlayer spacing(~0.95 nm)and high capacity as an example,we propose that the cycle life of vanadates can be greatly upgraded in AZIBs by regulating the concentration of ZnCl2 electrolyte,but with no need to approach“water-in-salt”threshold.With the optimized moderate concentration of 15 m ZnCl2 electrolyte,the KVO exhibits the best cycling stability with ~95.02% capacity retention after 1400 cycles.We further design a novel sodium carboxymethyl cellulose(CMC)-moderate concentration ZnCl2 gel electrolyte with high ionic conductivity of 10.08 mS cm^-1 for the first time and assemble a quasi-solid-state AZIB.This device is bendable with remarkable energy density(268.2 Wh kg^−1),excellent stability(97.35% after 2800 cycles),low self-discharge rate,and good environmental(temperature,pressure)suitability,and is capable of powering small electronics.The device also exhibits good electrochemical performance with high KVO mass loading(5 and 10 mg cm^-2).Our work sheds light on the feasibility of using moderately concentrated electrolyte to address the stability issue of aqueous soluble electrode materials.

Concentration of nitrogen molecules needed by nitrogen nanobubbles existing in bulk water

This paper investigates the stability of nitrogen nanobubbles under dif~ ferent concentrations of nitrogen molecules by molecular dynamics simulations. It is found that the stability of nanobubbles is very sensitive to the concentration of nitrogen molecules in water. A sharp transition between disperse states and assemble states of nitrogen molecules is observed when the concentration of nitrogen molecules is changed. The relevant critical concentration of nitrogen molecules needed by the existing nitrogen nanobubbles is analyzed.

Theoretical study on the stability of nanobubbles and its verification in molecular dynamics simulation

The stability of vapor nanobubbles in bulk liquid was investigated theoretically and the critical bubble size was derived from macroscale thermodynamic equations,below which the system destabilizes with sharp drop in pressure.This critical size was quantitatively verified in molecular dynamic simulation using the Lennard-Jones model of argon,where stronger attraction between the molecules at lower density is found to contribute most to the drop of system pressure and,as the Laplace pressure on the curved bubble interface fails to balance the pressure difference across the interface,the bubbles become unstable.The theoretical model could be extended to other systems where reliable equations of state and interfacial tension are available.

Surface nanobubbles on the hydrophobic surface and their implication to flotation

Nanobubbles play a potential role in the application of the flotation of fine particles.In this work,the identification of nanoentities was performed with a contact mode atomic force microscope(AFM).Moreover,the influences of setpoint ratio and amplitude of the cantilever and the responses of the formed surface nanobubbles to the fluctuation of pH,salt concentration,and surfactant concentration in the slurry were respectively studied.Nanobubbles were reported on the highly oriented pyrolytic graphite(HOPG)surface as the HOPG was immersed in de-ionized water under ambient temperature.The coalescence of nanobubbles occurred under contact mode,which provides strong evidence of the gaseous nature of these nanostructures on HOPG.The measuring height of the surface nanobubbles decreased with the setpoint ratio.The changes in the pH and concentration of methyl isobutyl carbinol(MIBC)show a negligible influence on the lateral size and height of the preex-isting surface nanobubbles.The addition of LiCl results in a negligible change of the lateral size;however,an obvious change is noticed in the height of surface nanobubbles.The results are expected to provide a valuable reference in understanding the properties of surface nanobubbles and in the design of nanobubble-assisted flotation processes.

An Adequate Perception on Attention Towards Stability and Obstacles of Space and Time, as an Assimilate Record of an Academic Chess

The current paper presents the objective test results of chess research carried out by the laboratory analysis of the Republic of Armenia. In order to identify the effectiveness of teaching academic chess, the research was carried out among the Armenian primary schools in 2-4 grades of high, medium, and low academic performance, concentration, and barriers to students＇ attention towards stability, response rates, as well as the moving objects. The focus of barriers to sustainability is put on appraisal methods of analysis, it is clear that the barriers to sustainability assessment criteria are low, among the 4th grade students medium and high academic performance, there was an apparent increase in the number of true confrontation. Therefore, the stability of the learners＇ attention was increasing. The ＂counter the moving object＂ methodology results suggest that Reaction to Moving Object coefficient, which is equal to the number of delays and early confrontation quotient, is gradually decreasing, adding the exact number of confrontation. The aim of teaching academic chess at schools is to develop teaching and students＇ cognitive sphere, in particular, logical thinking, imagination, analyzing capacity, thus contributing to the academic study of other subjects.

The existence and stability of bulk nanobubbles:a long-standing dispute on the experimentally observed mesoscopic inhomogeneities in aqueous solutions

In theory,nanobubbles can stably exist with a lifetime of microseconds at most,but numerous experimental observations demonstrate that nanobubbles in bulk solution can be stable from hours to weeks.Although various conjectures on the stability mechanism of bulk nanobubbles,such as the contaminant mechanism,skin mechanism,surface zeta potential mechanism,are proposed,there has not yet been a unified conclusion.Since bulk nanobubbles show great potential in a wide spectrum of applications and are relevant to a number of unsolved questions on cavitation and nucleation,the debate over their stability mechanisms has been active.In the past,extensive studies have been carried out to understand the mechanism of nanobubble stability,and important insights have already been provided.This paper will provide a brief overview of our current understanding of the unexpected stability of bulk nanobubbles.

Effects of pH on rheological characteristics and stability of petroleum coke water slurry

In this study, the effects of pH on slurrying properties of petroleum coke water slurry（PCWS） were investigated. The slurrying concentration, rheological characteristics and stability of PCWS were studied with four different types of additives at pH varying from 5 to 11.The results showed that the slurrying concentration, rheological characteristics and stability of PCWS all increased at first and then decreased with increasing pH from 5 to 11,and a pH of around 9 was found to be the most favorable acid–alkali environment to all these three slurrying properties. It was also indicated that only in a moderate alkaline environment can the additives be active enough to react with particle surfaces sufficiently to obtain good slurrying concentration and form a stable three-dimensional network structure, which can support strong pseudoplastic characteristics and good stability. An acid environment was a very unfavorable factor to the slurrying properties of PCWS.

Luminescence properties of Eu^(2+) -doped Ba_3Si_6O_12N_2 green phosphor: concentration quenching and thermal stability

The efficient Eu2＋ -doped Ba3 Si6O12N2 green phosphors were prepared by a traditional solid state reaction method under N2 /H2 atmosphere at a temperature up to 1350 ℃ for 12h. Photoluminescence （PL） properties showed a broad emission band with a peak of 525 nm and the full width of half-emission maximums （FWHM） of 70 nm under 460 nm light irradiation. The X-ray diffraction patterns （XRD） and scanning electron microscope （SEM） images of the synthesized powder demonstrated its pure phase and excellent crystallization. Quenching concentration in this phosphor was found to be 0.3. The mechanisms of concentration quenching and redshift of emission peak with increasing concentration of Eu2＋ were studied. The temperature dependence measurement of this green phosphor revealed excellent thermal quenching property compared to silicate green phosphor. It is believed that Ba3 Si6O12N2 ：Eu2＋ is an excellent green phosphor for UV or blue chip based white LEDs.

Multiplicity of thermodynamic states of van der Waals gas in nanobubbles

The gas-containing nanobubbles have attracted extensive attention due to their remarkable properties and extensive application potential.However,a number of fundamental aspects of nanobubbles,including thermodynamic states for the confined gas,remain still unclear.Here we theoretically demonstrate that the van der Waals(vd W)gases confined in nanobubbles exhibit a unique thermodynamic state of remarkably deviating from the bulk gas phase,and the state transition behavior due to the sizedependent Laplace pressure.In general,the vd W gas inside nanobubbles present multiple stable or transient states,where 0–2 states are for supercritical gas and 0–4 for subcritical gas.Our further analysis based on Rayleigh–Plesset equation and free energy determination indicates that the gas states in nanobubbles exhibits different levels of stability,from which the coexistence of multiple bubble states and microphase equilibrium between droplets and bubbles are predicted.This work provides insight to understand the thermodynamic states appeared for gas in nanobubbles.

Formation of nanobubbles generated by hydrate decomposition:A molecular dynamics study

Natural gas hydrate is estimated to have huge reserves. Its exploitation can solve the global oil and gas shortage problem. Hydrates decompose into water and methane, and methane molecules are supersaturated to form nanobubbles.Methane nanobubbles can affect the decomposition efficiency of hydrates. They can provide abundant methane sources for the re-nucleation of hydrates. Molecular dynamics is employed in this study to investigate the decomposition process of type I methane hydrate and the formation of methane nanobubbles generated during decomposition under different methane mole fraction, pressures, and temperatures. The results indicate that external pressure inhibits the diffusion of methane molecules, thereby preventing the formation of nanobubbles. A higher mole fraction of methane molecules in the system requires a higher external pressure to generate stable nanobubbles after the decomposition of the hydrate structure.At 330 K, it is easy to form a nanobubble structure. Results of this study can help provide ideas for the study of efficient extraction and secondary nucleation of hydrates.

Role of substrate softness in stabilizing surface nanobubbles

The contact line pinning and supersaturation theory for the nanobubble stability has attracted extensive concerns from experimental investigators,and some experimenters argue that the contact line pinning is unnecessary.To interpret the experimental observations,we have proposed previously through molecular dynamics simulations that the deformation of soft substrates caused by surface nanobubbles may play an important role in stabilizing surface nanobubbles,while yet no quantitative theory is available for explanation of this mechanism.Here,the detailed mechanism of self-pinning-induced stability of surface nanobubbles is investigated through theoretical analysis.By manipulating substrate softness,we find that the formation of surface nanobubbles may create a deformation ridge nearby their contact lines which leads to the self-pinning effect.Theoretical analysis shows that the formation of nanobubbles on sufficiently rigid substrates or on liquid-liquid interfaces corresponds to a local free energy maximum,while that on the substrates with intermediate softness corresponds to a local minimum.Thus,the substrate softness could regulate the surface nanobubble stability.The critical condition for the self-pinning effect is determined based on contact line depinning,and the effect of gas supersaturation is explored.Finally,the approximate stability range for the surface nanobubbles is also predicted.

Application of UPLC-QTOF-MS Technology in Quality Stability Evaluation of Moluodan Concentrated Pills

[Objectives]To use liquid chromatography-mass spectrometry technology to analyze the chemical composition of traditional Chinese medicine and explore its application in the evaluation of quality stability of traditional Chinese medicine.[Methods]Ultra performance liquid chromatography-quadrupole time-of-flight mass spectrometry(UPLC-QTOF-MS)was used to detect the samples of Moluodan concentrated pills.By comparing and analyzing the detection results of 10 different batches of Moluodan concentrated pills,combined with principal component analysis(PCA),the quality stability of Moluodan concentrated pills was evaluated.[Results]A total of 367 chemical components were identified in Moluodan concentrated pills.The average repetition rate of the chemical components contained in the 10 different batches of samples reached 92%.The overall quality stability of the Moluodan concentrated pills was good.[Conclusions]The UPLC-QTOF-MS technology combined with PCA provides a reference for the overall quality evaluation of Moluodan concentrated pills,and provides new detection methods and ideas for the analysis of the components of Chinese medicine.

Effects of in-situ stress on the stability of a roadway excavated through a coal seam

Roadways excavated through a coal seam can exert an adverse effect on roadway stability. To investigate the effects of in-situ stress on roadway stability, numerical models were built and high horizontal stresses at varying orientations were applied. The results indicate that stress concentrations, roadway deformation and failure increase in magnitude and extent as the excavation angle with respect to the maximum horizontal stress increases. In addition, the stress adjacent to the coal-rock interface sharply varies in space and evolves with time; coal is much more vulnerable to deformation and failure than rock.The results provide insights into the layout of roadways excavated through a coal seam. Roadways should be designed parallel or at a narrow angle to the maximum horizontal stress. The concentrated stress at the top corner of the face-end should be reduced in advance, and the coal seam should be reinforced immediately after excavation.

Stability of Standing Waves for the Nonlinear Schrödinger Equation with Mixed Power-Type and Hartree-Type Nonlinearities

This paper studies the existence of stable standing waves for the nonlinear Schrödinger equation with Hartree-type nonlinearity i∂tψ+Δψ+| ψ |pψ+(| x |−γ∗| ψ |2)ψ=0, (t,x)∈[ 0,T )×ℝN.Where ψ=ψ(t,x)is a complex valued function of (t,x)∈ℝ+×ℝN. The parameters N≥3, 0p4Nand 0γmin{ 4,N }. By using the variational methods and concentration compactness principle, we prove the orbital stability of standing waves.

Luminescence,Concentration Quenching and Thermal Stability of White Emitting Phosphor Ba_2Ca(BO_3)_2:Dy^(3+)

A white emitting phosphor Ba2Ca(BO3)2:Dy3+ was synthesized via a high temperature solid state reaction at 1000℃ for 5 h. The luminescence, mole fraction quenching and thermal stability of Ba2Ca(BO3)2:Dy3+ were investigated. According to the phase composition analyzed by X-ray powder diffraction, there is no crystalline phase except Ba2Ca(BO3)2 in the sample. Ba2Ca(BO3)2:Dy3+ can produce white emission under 348 nm excitation. The emission intensities of Ba2Ca(BO3)2:Dy3+ are affected by Dy3+ concentration. The concentration quenching effect was analyzed, and the concentration quenching mechanism was verified as dipole-dipole interaction. The critical distance(R c) obtained based on the crystal structure data is 2.911 nm. At 150℃, the emission intensity of Ba2Ca(BO3)2:Dy3+ is 68.0% of the initial value at room temperature. The activation energy for the thermal quenching calculated is 0.202 e V. Moreover, the CIE chromaticity coordinates of Ba2Ca(BO3)2:Dy3+ locate in the white region of(0.319, 0.356).

Effects of ammonia concentration in hydrothermal treatment on structure and redox properties of cerium zirconium solid solution

Cerium zirconium solid solution is a key washcoat material for automotive three-way catalysts(TWCs).However,improving the redox ability and high temperature thermal stability of cerium zirconium solid solution is still a challenge.In this paper,the cerium zirconium solid solution was prepared by a coprecipitation-hydrothermal method,and the effects of the ammonia concentration on their structures and redox properties were investigated.The results show that when the ammonia concentration is 0.8 mol/L,the aged sample(1100℃/10 h)of cerium zirconium solid solution has the highest specific surface area of 23.01 m^(2)/g.Additionally,the increase of ammonia concentration improves the uniformity of phase compositions and increases the oxygen vacancies.When the ammonia concentration reaches 0.4 mol/L,the cerium zirconium solid solution exhibits the best redox activity,with the lowest reduction temperature of 565℃.Therefore,increasing ammonia concentration in the hydrothermal treatment is beneficial to the thermal stability and redox performance of cerium zirconium solid solution.

Qualitative analysis on adiabatic and dynamic stability of LTS/HTS hybrid conductor with concentric configuration

The I-V characteristic of a superconductor is generally described by power-law,in which the superconductor with a high n transfers quickly from superconducting state to the normal conducting state.With a high transport current,in the low n value area,flux flow voltage becomes lower than in the high n value area,so that the transient characteristics strongly affect its stability.Based on those properties,we propose a new hybrid conductor which is made of low temperature superconductor(LTS) and high temperature superconductor(HTS) with concentric configuration in which the HTS coat is located outside of the LTS core.According to their power-law models,the modified adiabatic and dynamic stability criteria are qualitatively obtained by taking account into not only their critical currents but also n values.As a result,the new hybrid conductors have potential applications with higher engineering current density and improved stability.